Optimal working-fluid selection for organic Rankine cycle integrated into a combined cycle cogeneration plant

Abstract

We examined how working-fluid properties impact the organic Rankine cycle (ORC) and bottoming cycle in a cogeneration system, and compared the sizes of turbines according to different working fluids. Working fluids R123, R245fa, and R245ca were selected based on factors such as the T-s diagram slope, environmental impact, and safety. The latent heat for vaporization significantly impacted ORC and bottoming-cycle performance. R123 produced the lowest bottoming cycle output of 38.49 MW and an ORC output of 1.95 MW. R245ca required a bigger turbine size, leading to the largest volume flow rate of 20 m3/s at the ORC turbine outlet. The bottoming-cycle output was 38.68 MW and the ORC generated 2.61 MW, which were the highest. R245fa showed promise in terms of compact turbine size due to its smallest volume flow of 14.96 m3/s at the ORC turbine outlet, even though the overall output was 250 kW lower than that of R245ca.